Messages in this thread | | | Date | Thu, 17 Sep 2015 18:07:05 +0100 | From | Catalin Marinas <> | Subject | Re: [PATCH v2] arm64: Introduce IRQ stack |
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On Thu, Sep 17, 2015 at 09:36:04PM +0900, Jungseok Lee wrote: > On Sep 17, 2015, at 7:33 PM, James Morse wrote: > > On 16/09/15 12:25, Will Deacon wrote: > >> On Sun, Sep 13, 2015 at 03:42:17PM +0100, Jungseok Lee wrote: > >>> diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h > >>> index dcd06d1..44839c0 100644 > >>> --- a/arch/arm64/include/asm/thread_info.h > >>> +++ b/arch/arm64/include/asm/thread_info.h > >>> @@ -73,8 +73,11 @@ static inline struct thread_info *current_thread_info(void) __attribute_const__; > >>> > >>> static inline struct thread_info *current_thread_info(void) > >>> { > >>> - return (struct thread_info *) > >>> - (current_stack_pointer & ~(THREAD_SIZE - 1)); > >>> + unsigned long sp_el0; > >>> + > >>> + asm volatile("mrs %0, sp_el0" : "=r" (sp_el0)); > >>> + > >>> + return (struct thread_info *)(sp_el0 & ~(THREAD_SIZE - 1)); > >> > >> This looks like it will generate worse code than our current implementation, > >> thanks to the asm volatile. Maybe just add something like a global > >> current_stack_pointer_el0? [...] > --- a/arch/arm64/include/asm/thread_info.h > +++ b/arch/arm64/include/asm/thread_info.h > @@ -77,7 +77,7 @@ static inline struct thread_info *current_thread_info(void) > > asm volatile("mrs %0, sp_el0" : "=r" (sp_el0)); > > - return (struct thread_info *)(sp_el0 & ~(THREAD_SIZE - 1)); > + return (struct thread_info *)sp_el0; > }
This makes sense, since we just use sp_el0 as a scratch register, store the current thread_info address directly. But, as James mentioned, I don't think you need asm volatile, just asm (it has a small impact in my tests).
-- Catalin
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